Apparatus for supporting cathode heaters

ABSTRACT

A heater support ring for use in the multicathode gun of a cathode ray tube. The support ring is made from a single piece of conductive wire which is preformed into a generally triangular shape the apex portions of which are glassed into gun assembly rods. Three cuts are then made in the wire and free ends adjoining the cuts are bent into position to accept the connections of the filamentary heaters. The support ring structure is unusually short, in the direction of the axial length of the cathode ray tube gun, and few welds are required.

Elnite States Patent [191 Chesla APPARATUS FOR SUPPORTING CATHODE HEATERS [75] Inventor: Thomas E. Chesla, Chalfont, Pa.

[73] Assignee: Philco-Ford Corporation,

Philadelphia, Pa.

[22] Filed: May 14, 1973 [21] Appl. No.2 360,152

Related US. Application Data [62] Division of Ser. No. 256,980, May 25, 1972, Pat. No.

[52] US. Cl. 313/273, 313/277 [51] Int. Cl. H01j 1/92 [58] Field of Search 313/272-273, 313/277, 264, 333

[56] References Cited UNITED STATES PATENTS 980,703 l/19l1 Thomson 313/277 1,069,707 8/1913 Krause 313/277 [11] 3,835,344 [451 Sept. 10,1974

3/1966 Brown ..313/272 10/1973 Werst ..313/277 Primary Examiner-James W. Lawrence Assistant Examiner-Wm. H. Punter Attorney, Agent, or Firm-Robert D. Sanborn; Carl H. Synnestvedt; Harry W. Hargis, lll

[5 7] ABSTRACT A heater support ring for use in the multicathode gun of a cathode ray tube. The support ring is made from a single piece of conductive wire which is preformed into a generally triangular shape the apex portions of which are glassed into gun assembly rods. Three cuts are then made in the wire and free ends adjoining the cuts are bent into position to accept the connections of the filamentary heaters. The support ring structure is unusually short, in the direction of the axial length of the cathode ray tube gun, and few welds are required.

1 Claim, 6 Drawing Figures APPARATUS FOR SUPPORTING CATHODE HEATERS This is a division of application Ser. No. 256,980, Filed May 25, 1972, now US. Pat. No. 3802855.

BACKGROUND OF THE INVENTION This invention relates to electron guns, and is especially concerned with improvements in the structure and fabrication of filamentary heaters used in electron guns of color cathode ray tubes. In the manufacture of guns of this type, it has been customary to form the heater support structure, commonly known as the support ring, of a plurality of pieces of wire or strap material. Adjacent spaced end portions of each of said pieces is glassed into the assembly rod, while opposite adjacent end portions are welded to the heater connections. In some instances the construction has even been complicated by the use of studs, welded to the ring and embedded in the glass of the bead. Such constructions are disadvantageous in that they involve a large number of individual welds, typically 13 or more, each of which welds increases the problems of assembly and is a potential source of arcing. Due to the considerable number of individual pieces which must be fabricated into the heater support ring, such prior art structures have frequently been made of relatively wide ribbon-like conductors in order to insure the necessary rigidity. Such wide conductors increase the length of the gun structure.

It is the general objective of the present invention to provide an improved heater support ring, in the fabrication of which a single piece of wire may be used. The wire is generally triangular, when viewed in plan, and the number of welds is reduced very substantially, for example from thirteen to eight.

SUMMARY OF THE INVENTION In achievement of the foregoing as well as other objectives and advantages of my invention, I shape a piece of nickel or stainless steel wire into the aforesaid generally triangular configuration, in; which two adjacent corners are formed by a continuous run of the wire, bent reversely upon itself. The free ends of the loop are disposed in close adjacency. These free ends have outturned portions. The wire is then held in an assembly jig, and metal of each of the three corners is inserted into the glass, as part of the conventional beading operation. Three such beads extend along and support the various elements of the gun structure. The configuration of the wire ring at each corner results in solidly locking the wire into the glass, thereby eliminating any possibility of twisting.

After the wire is embedded in the beads, it is cut in three places intermediate the apexes of the triangle, and the adjacent cut ends are spread and formed to provide support for connections extending down from the usual ceramic coated wire which comprises the filamentary heaters. While a support ring formed of wire of small cross section, either square or circular, results in the greatest degree of shortening of the gun structure, the invention also contemplates that the ring may be formed of narrow ribbon, if desired.

In summary, the heater support of this invention reduces the cost of the cathode ray tube gun by utilizing less material and simplifying the fabricating process. Also. the invention reduces the number of welds, and

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary elevational view, with parts broken away, showing the cathode heater support structure of this invention disposed in the neck of a cathode ray tube;

FIG. 2 is a plan view of the cathode ring or loop of my invention as it appears prior to association with the glass insulators which support the gun structure;

FIG. 3 is a view similar to FIG. 2 and illustrating techniques utilized in assembling the structure;

FIGS. 4 and 5 are views similar to FIG. 3 and illustrating steps in the fabrication process which are applied subsequent to the steps illustrated in FIG. 3; and

FIG. 6 is a side elevation of a support ring after glassing thereof, illustrating the mode of attachment of a friamentary heater thereto.

DESCRIPTION OF THE PREFERRED PRACTICE OF THE INVENTION With particular reference to the drawing, there is shown in FIG. 1 a cathode support ring 10 made according to the invention and shown as mounted in the neck 11 of a color cathode ray tube 12. Portions of the neck are broken away in the interest of clarity, and illustration is limited to the three vitreous insulator rods, shown at 13, 14 and 15, and to the cathode heater ring which is associated with and supported by said rods. As will be understood, a complete gun structure would also comprise a battery of three electron guns, including grids and other elements, all of which would be supported by the vitreous rods. All of the tube elements, including the cathode heaters, would have suitable connection to the terminal pins 16 which extend externally of the tube. The cathode heaters appear in the drawing at l7, l8 and 19 and are preferably of the known type which comprise twisted ceramic coated wire' each nested within a narrow, tubular, cathode enclosure C.

The enclosures C are shown broken-away, to illustrate or loop 10 is generally triangular when viewed in plan,

see for example FIG. 2, and includes two comer-portions which are formed integrally with the conductor of which the loop is made and which comprise a portion of the wire bent reversely upon itself, as appears at 22 and 23. These two corners are embedded'in the vitreous rods 13 and 15, in accordance with known techniques, the rods being held in suitable assembly jigs. It will be appreciated that the fact that the wire is uninterrupted within the rods 13 and 15 is of advantage in that it eliminates the short jumper wires usually used and which require welding to the legs of the loop 10, in order to insure a series circuit therethrough. The third corner of the generally triangular loop is formed by free ends 24 and 25 of the wire loop, disposed in closely spaced adjacency, and embedded in the third vitreous rod 14. To promote rigidity in mounting, each of the free ends 24 and 25 carries a short laterally extending projection (24a, 25a, FIG. 2) which are embedded in rod 14.

In the fabrication of a cathode heater structure of this kind, that is a heater structure for use in a generally cylindrical electron gun including three cathodes disposed in generally triangular array, the following unique steps are emphasized herein, as being of particular importance. First, there is provided the single unitary loop of conductive wire, of generally triangular configuration when viewed in plan, and in which two adjacent corners are each formed by the reversely bent wire portions shown at 22 and 23. It is a feature of the invention that the bending is done in such a way as to include at each corner a short course of wire which extends perpendicularly to the adjacent loop portions which enter the vitreous rod. These portions extend rectilinearly within the glass rod for locking engagement therewith. This feature will be clearly understood by comparison of FIGS. 2 and 3.

The third comer of the loop is formed by the abovementioned free ends 24 and of the wire loop which are disposed in closely spaced adjacency and also embedded in one of the rods (rod 14).

As is suggested in FIG. 3, the wire of the loop, supported as it is by the three rods within which its corners have been glassed, is then severed at points intermediate the corners of the triangular figure. Convenient lines of severance are shown in FIG. 3 at 26, 27 and 28.

Another important step of this invention is illustrated in FIG. 4 and involves configuring the wire in the region of the severed portions to separate the adjacent severed ends thereof, see for example the severed ends 29 and 30, and thereby to provide support locations for connections to the filamentary heaters. The three heaters, 17, 18 and 19 are then connected in series circuit through the agency of the wire of loop 10, by welding the two leads of each such heater to a corresponding pair of spaced severed ends. The resultant heater structure is illustrated in plan in FIG. 5, and in elevation in FIG. 6. The latter figure shows the heater structure disassociated from the neck of the tube and with only two of the vitreous rods shown, in the interest of clarity of illustration. The manner in which the leads 20 and 21 are connected, as by welding, to the adjacent severed ends 29 and 30 of the wire loop is clearly shown in this figure.

In one representative heater structure fabricated in accordance with this invention, the wire of the loop had a circular cross section equal to 0.020 inch. A gap equal to 0.060 inch was provided between the courses of wire which enter the vitreous rods. The location of this gap is illustrated at 31 in FIG. 2. The purpose of the gap, which is proportional to the size of the wire being used, is to allow the glass bead to fold over and completely envelope the rectilinear runs of wire 22 and 23. This ensures that the wire is properly locked within the rod. The insertion and locking step can be practised with the rods jigged to stand either vertically or horizontally. The result will still be the same.

As will now be appreciated, the invention has the important advantage of achieving an unusually rigid heater ring or loop, with a minimum number of welds. Other than the welding of the individual heater leads 20 and 21 to the wire loops, the only other required welds are the two which secure the supply conductors 32 and 33 to the loop in the region of the mentioned third corner. The location and securement of these supply conductors is shown in FIG. 5.

While very good results have been obtained utilizing the mentioned dimensions, the invention is, of course, not to be understood as limited thereto. Also, the wire of the loop might be square in cross section, or if desired could comprise a narrow ribbon. The term wire, as employed in this disclosure and the appended claims, should be understood as including within its scope conductors of any desired cross section, for example conductors comprising a narrow ribbon.

l. A cathode heater loop, comprising: a conductive wire having three cornerportions disposed in generally triangular array when the loop is viewed in plan, and presenting gaps in each of three regions intermediate said corner portions, two of said corner portions being formed by a section of the wire reversely bent upon itself and the third corner portion being formed by free ends of the wire loop disposed in closely spaced adjacency; three vitreous rods each of which has embedded therein one of said corner portions; three filamentary heaters supported by said wire loop and each of which heaters has a pair of leads connected across a corresponding one of said gaps; and said loop being further characterized in that said two corner portions include short courses of wire extending perpendicularly to those portions of the loop which enter the vitreous rod, said short courses lying in the plane of said loop and being embedded in said vitreous rod, and said portions which enter the vitreous rod being spaced apart at the region of entry into the rod. 

1. A cathode heater loop, comprising: a conductive wire having three corner portions disposed in generally triangular array when the loop is viewed in plan, and presenting gaps in each of three regIons intermediate said corner portions, two of said corner portions being formed by a section of the wire reversely bent upon itself and the third corner portion being formed by free ends of the wire loop disposed in closely spaced adjacency; three vitreous rods each of which has embedded therein one of said corner portions; three filamentary heaters supported by said wire loop and each of which heaters has a pair of leads connected across a corresponding one of said gaps; and said loop being further characterized in that said two corner portions include short courses of wire extending perpendicularly to those portions of the loop which enter the vitreous rod, said short courses lying in the plane of said loop and being embedded in said vitreous rod, and said portions which enter the vitreous rod being spaced apart at the region of entry into the rod. 